I need some help. I replaced 2-type 24 batteries with 2-type 27 marine/rv batteries. With these new type 27 batteries, I blew my refridgerator fuse (15 amp) and several light bulbs blew when left on too long. Am i not able to switch from type 24 to type 27 batteries or do i need specifically type 27 RV batteries?

Is it possible you connected these incorrectly? 12 volt batteries connected in parallel are positive to positive, negative to negative.

Yes - it does sound like maybe a connection issue. One other thing to check - make sure the positive and negative wires from the trailer aren't reversed. Different manufacturers have different systems, but on our old camper the positive wire was black, which is the opposite of typical house wiring. Reversing those will blow fuses.

thanks for the info. To rbneron, I was only hooked up to battery. To triguy, from your response, i hooked my batteries up wrong. i had the batteries hooked up in series with main line going to pos, the connector going from the neg to pos, and then the other main line going to neg.

If the batteries are hooked up incorrectly you could be putting 24 volts into your TT system and this can do a lot of damage, double check as Triguy stated above. Unhook the battery until you are sure it is connected properly again as Triguy stated.